Electric motors and the like designed to move vehicles on the ground have been used for some time, often in combination with internal combustion or other engines in hybrid vehicles, although more recently these motors alone have been proposed for driving vehicles. The use of electric motors to power a range of vehicles, from automobiles to buses, has been suggested. Equipping aircraft wheels with motors to move aircraft on the ground without reliance on the aircraft's main engines has also been proposed. Aircraft with one or more wheels powered by an electric or other motor are, ideally, able to taxi autonomously between landing and takeoff under only the power provided by these motors. Although the use of “electric taxi” to move an aircraft on the ground has been described, precisely controlling the electric or other motors suggested for this purpose so that the motors can actually operate with optimum efficiency at taxi speeds has not been suggested.
Dilmagahni et al, in U.S. Patent Application Publication No. 2009/0218440, describe a control system for a powered wheel system for aircraft with two or more motors coupled to aircraft wheels that are independently controlled to move an aircraft on the ground during forward and reverse taxi. The rotary speeds and direction of rotation of the driven aircraft wheels are determined and controlled to steer the aircraft, boost the aircraft's brakes when the motors are decoupled from the wheels, and pre-spin the aircraft's wheels prior to landing. It is not suggested that specific operating parameters of the preferred brushless electric motors other than rotary speed and direction of rotation could, or should, be defined or controlled to optimize aircraft taxi. In U.S. Patent Publication No. 2010/0276535, Charuel et al describe a method of taxiing an aircraft that employs a main taxiing motor, preferably a permanent magnet motor, in at least one aircraft nose wheel and an auxiliary taxi motor in at least one main wheel. A taxiing computer adjusts power first to auxiliary motors and then to main motors. Power supplied to the motors is continuously adapted so that torque delivered to auxiliary motors is reduced to zero when the auxiliary motors are no longer needed to assist the main motors in moving the aircraft. Auxiliary motors are provided with only sufficient power to ensure that they do not generate any resistive torque opposing movement of the aircraft. The control of torque or other parameters of the main taxi motor is not mentioned.
In U.S. Pat. No. 6,150,780, Young et al describe an electric drive system for vehicles, specifically haul trucks, with AC motorized wheels and a motor control that uses motor torque and torque limits and engine horsepower and horsepower limits instead of engine speed to control vehicle travel. The torque available from each wheel motor is based on its respective speed, and the available maximum torque for each wheel motor is determined based on the speed of that individual wheel motor. It is not suggested, however, that this system would function solely with wheel motors in the absence of the operation of the vehicle engine or that motor torque could be determined and controlled in the absence of engine horsepower.
Moving a taxiing aircraft by onboard non-engine drive means, particularly electric drive means, requires the precise determination and control of torque and other drive means parameters to optimize taxi and to extend the operational life of drive means components. Consequently, a need exists for a system and method for defining and controlling torque and other drive means parameters required to produce an optimum aircraft taxi profile and thereby optimize aircraft ground travel.